Brake Problems on a 71 Mach 1

[71 Mach 1]

My rear brakes are not getting any fluid. The front work fine, I bled them and everythings works, so I am assuming the proportioning valve is okay. When I hit the brakes the front resevoir bubbles but when I disconnected the brake line into the rear axle no fluid is present. Any help would be appreciated. Oh yeah, it has power brakes and I have tested it with the engine off.

Thanks
John

[Mil1ion]

Has the car been sitting doing nothing for any length of time ?

[71 Mach 1]

yes, for at least 4 years.

[SaleenFiend]

I would check all of the lines to make sure nothing is leaking when going toward the rear. You have a pretty wide spectrum here and I would start with the process of elimination.

Correctly bleed master cylinder: Pull The lines off of the master cylinder and fill the reservoir. Plug one hole in the cylinder with your finger (may need an extra pair of hands to help) and bleed one hole at a time just like you would the brakes until fluid is coming out. Once you have fluid out of the front hole hook up the line. Do the same for the next hole.
If you are able to bleed the master cylinder then it is O.K.

Then follow the lines throughout the vehicle as you check for leaks or clogs. I would remove the lines from the Proportioning Valve and bleed as you did the master cylinder just to check its operation.

I'm no expert on this but I would assume you would want to check all the lines at every point possible to eliminate the area of blockage or failed parts.

[71 Mach 1]

Thank a lot for the suggestions, I have bled the front discs and they are fine. I replaced most of the rear lines (except the one that runs the length of the car). I think my problem may be with the "plunger" that is set every time the brake light goes on during start-up.

[Mil1ion]

Because brake fluid absorbs moisture and the car has sat.. IMO, you need to remove the proportioning valve and clean it out or replace it because it has probably has rusted inside.

This is a common theme for cars that sit in a somewhat humid condition.

[71 Mach 1]

Thanks, that is a good idea, I think I will pull the valve and clean it thorroughly.